N = int(input())
C = list(input())
C_ = sorted(C)

wr = rw = 0
for i in range(len(C_)):
    if C[i] != C_[i]:
        if C[i] == 'R' and C_[i] == 'W':
            rw += 1
        else:
            wr += 1

print(max(wr, rw)) N = int(input()) N int(input()) int input() input C = list(input()) C list(input()) list input() input C_ = sorted(C) C_ sorted(C) sorted C wr = rw = 0 wr 0 = rw = 0 rw 0 for i in range(len(C_)):
    if C[i] != C_[i]:
        if C[i] == 'R' and C_[i] == 'W':
            rw += 1
        else:
            wr += 1 i range(len(C_)) range len(C_) len C_ if C[i] != C_[i]:
        if C[i] == 'R' and C_[i] == 'W':
            rw += 1
        else:
            wr += 1 C[i] != C_[i] C[i] C i C_[i] C_ i if C[i] == 'R' and C_[i] == 'W':
            rw += 1
        else:
            wr += 1 C[i] == 'R' and C_[i] == 'W' C[i] == 'R' C[i] C i 'R' C_[i] == 'W' C_[i] C_ i 'W' rw += 1 rw 1 wr += 1 wr 1 print(max(wr, rw)) print max(wr, rw) max wr rw wr += 1 1 wr N = int(input()) int(input()) N wr = rw = 0 0 wr C_ = sorted(C) sorted(C) C_ rw += 1 1 rw rw = 0 0 rw C = list(input()) list(input()) C
N = int(input())
C = list(input())
C_ = sorted(C)

wr = rw = 0
for i in range(len(C_)):
    if C[i] != C_[i]:
        if C[i] == 'R' and C_[i] == 'W':
            rw += 1
        else:
            wr += 1

print(max(wr, rw))
